Lapping or abrading tool



May 16, 1939.

W; E. HOKE LAPPING OR ABRADING TOOL Filed July 27, 1937 2 Sheets-Sheet lMay 16, 1939. w, HOKE 2,158,123

LAPPING 0R ABRADING TOOL Filed July 27, 1937 2 Sheets-Sheet 2 A UNITEDSTATES PATENT OFFICE.

2,158,123 .LAPPING on ABRADING 'rooL William E. Hoke; Baltimore, Md.Application July 27, 1937, Serial No. 155,845 4 Claims; (01. 51-206) IFuel pumps and injection'nozzles of small size high speed Diesel enginesmust function witha high degree of accuracy, in view of the very smallquantities of fuel injected for each working stroke ofthe engine. Inthecase of an engine running at 2000 R, P. M. injection may have to becompleted in about .002 of a second and if the engine is of a four cycletype, each fuel pump and injection nozzle must go through the injectionprocess 1000 times per minute. 11. the engine is of the two cycle type,at 2000 R. P. M., injection must occur 2000 times per minute for eachcylinder. The sizes of the fuel pump and injection nozzle of such anengine are so small that it is not practical to use piston rings orother means to insure accurate fitting. The plungers and cylinders mustbe lapped with a clearance not to exceed .0001 of an inch and to obtainsuch accuracy has been a very diflicult problem in this art heretofore.The outer cylindricalmember of the injection nozzle and fuel pump arenot only hardened but nitrided before being lapped for final use. Thehardening process, if done after the lapping, would so warp the surfacesthat they would lose their accuracy of flt, and cause leakage.

By my two patents both dated March 11, 1924,

and numbered 1,486,338 and 1,486,344processes and mechanism for lappinga number of articles drical surfaces of an accuracy of 1,000,000th-, of

- in a plurality of such bores. If a plurality of such and finishingthem so that they are identical has been set forth. These processes andthe mechanismmay be'used to make the pistons of the fuel pump and of theinjection nozzle but up to the present time no method has been known formaking the inner cylindricalsurfaces of the fuel pump and of theinjection nozzle accurate in their fit with the pistons. Previouspractice has been to make a plurality of pistons and then finish eachcylindrical part to fit that particular piston and this process is notonly very tedious but also very expensive. Y

By the processes of this invention inner cylinan inch can be obtainedand numbers'of such cylinders may be made at one time, which are-allidentical, to thereby avoid the necessity of fitting each cylinder o'rbore 7 to a respective piston. Accurate fitting of cylinders and pistons.will prevent leakage even at the high pressure of 800 pounds per squareinch to which the pumps and nozzles are subjected.

The invention utilizes the symmetrical distribution of errors to correctthe errors occuring some are too small, perhaps each of varying degreeand perhaps some are the correct. size. These may all be brought to aproper and identical size by lapping. 7 If each bore is lapped a smallquantity in a regular sequence or order with the 5 same lap a smallamount of metal is taken from each bore that is too smalland the boresalready at size are not affected by the passage of the lap. The amountof lapping given to each cylindrical surface is so small as scarcely tomake any wear 10 on the lap itself. The sequence of the lapping of thegroup of bores may be varied in any predeter- 'mined manner so that allof the errors occurring in the sizes of the bores may be finallyeliminated, by successively lapping and varying the sequence.

The lap usually consists of a cylindrical member substantially the' sizeof the cylindrical surfaces to be lapped, made of wax, wood, lead,

' aluminum or copper or some such material havthis lap of a materialhaving a differential thermal expansion from the metal of the bores sothat in the warming of the lap andthe bores the lap will expand morerapidly than the bores and thereby cause the lap to continue itsabrading action on the bore. When it is desired. to lessen the abradingaction of the lap on the bore the bore and lap will be cooled, and themetal of the bore contracting more rapidly due to the cooling willthereby lessen the abrading' action of the lap on the bore.

In the use of the usual cylindrical lap there is a tendency for the lapto wear unequally and thereby to bell-mouth. the cylindrical surfacebeing lapped. In lapping the part of the cylindrical surface furthestremoved from the lap entry and exit end, the complete length of the lappasses the entry and exit end more often and consequently gives it morelapping than the far end. This wearing effect on the lap and the unequallapping of the lap entry and exit end may be partially overcome bymaking the laps slightly shorter, when working in a blind bore, than thecylindrical surfaces so that the closed end of the bore may beabraded'slightly more than the open end byabrading with the complete lapwithin the cylindrical surface. When the bore being abraded is open atboth ends a lap only slightly longer than the cylindrical opening may beused and the abrading action made greater at the end of the bore awayfrom thelap support than at the entry and exit end, that toward the lapsupport,

so as to equalize the abrading at the far end of the cylindrical surfacewith. the excess lapping obtained on the entry and exit end of thatsurface due to the passage of the complete lap along that end, or thebore may be reversed end for end.

The lap may also be made in two parts, transversely, and. attachedtogether at their ends and also to the support. By varying the relativepositions of the two sections of the lap or by reversing the full lap onits support a more equal wear With these and other objects andadvantages in view, the invention consists of the features ofconstruction and operation and the methods described in the followingspecification and illustrated in the accompanying drawings in which adiagrammatic form of an apparatus embodying the essentials of themechanical features of the invention are shown. Also there are shownillustrative arrangements of the lap to obtain the purposes of theinvention.

Referring to the drawings:

Figure 1 is a plan view of an apparatus for holding a plurality ofarticles to be lapped.

Figure 2 is a side view of the same withthe container wall shown insection.

Figure 3-is a detailed view of a catch to hold the article clampingmeans in place.

Figure 4 is a view of a lap showing a flexible connection with itsarbor.

Figure 5 is a similar view showing a modified form of connection.

Figure 6 is a further modified form of lap shown lapping an open-endedarticle.

Figure '7 is a sectioned lap operating on a similar article.

Figure 8, is a view of the top of the lap shown in Fig. 'I with thearbor removed.

Figure 9 is a view of the sectioned lap operating on a blind-endedarticle.

Figure 10 is an enlarged view of an alternate form of connection of alap with its arbor.

Figure 11 is a plan view of the lap shown in Fig. 10 with its arborremoved.

In Figs. 1 and 2, the container I having therein a liquid or other heattransfer fluid, has a standard-2 at its center supporting a plate 3freely rotating On ball bearings 4. This plate 3 has a. pluralityofopenings 5 arranged symmetrically therein and each opening 5 has anindex number 6. In each opening 5, and there are shown 36 of suchopenings, there is placed the article I to be lapped. In these viewssuch articles are shown to be injection nozzles for Diesel engines. Asshown these nozzles have a closed or blind lower end and an open entryand exit end with a shoulder 8 which rests upon the plate 3. The plate 3is cut away as shown at 9 to facilitate uniformity of heat transfer.

The standard 2 has projecting from its center, standard ill on which ispivoted lever II. The container I has preferably equally distributedaround its diameter three supports l2 which serve to maintain the plate3 in a horizontal position. Over one of these supports 12 and hinged totheside of the container l is a clamp l3 which has in its center, whenhorizontal, a vertical opening l4 substantially the size of the bore ofthe article to be lapped. This opening is slightly flared at its top i5to form a lead for the lap. The lower portion of the clamp I3,concentric with the opening M, has a gripping opening IE .to firmlyclamp the article to be lapped against the plate 3. The clamp l3 at itssides is cut out as shown at H to avoid striking adjacent articles. Theclamp l3 has at its free end a link l8 pivoted for free vertical angularmovement therein, and at the top this link has an elongated slot'l9therein to allow free vertical movement of a pivot 20 in the lower endofthe lever II. This link l8 has surrounding it a spring which bearsagainst clamp l3 and the free play allowed by the slot l9 allows thelower end of the lever II to resiliently press the clamp l3 upon the topof one article I. The other end of this lever H is heldin "thisresilient holding position by a catch 2| pivoted to a standard 22 on thecontainer wall], as shown in Fig. 3. The liquid level in the containeris preferably above the top of the articles I and paddles 22a may beplaced on the bottom of plate 3 to slightly agitate the liquid to makemore uniformthe transfer of heat therethrough. An electric coil 23 isplaced in the bottom of the container in order to heat the liquid to agiven amount and to maintain the temperature that is desired. Thiselectric coil 23 may be energized through a thermostaticallyoperatedswitch 24 which is operated by the thermostat bulb 25 placed in thebottom of the container and preferably in the neighborhood of thearticle being lapped. As a guide to the operator a thermometer 26 mayalso be in the liquid.

When it is desired to lower the temperature of the fluid this could bedone by any mechanical means or the fluid therein, which is preferablysome neutral oil, could be withdrawn through a valve or outlet 21 andcolder fluid placed in the container.

Practically any form of drill press may be used having a chuck to holdthe lap and to rotate it and to allow it to be raised and lowered at thewill of the operator.- In Fig. 2 a chuck 28 is shown containing a lap 29held by its arbor 30 in the chuck.

In Fig. 4 an arbor 30 is shown having a key 3| which may be driventightly therein and removed at will. The lap 29 shown in this View has aslightly enlarged centralbore 32 to allow free play of the lapon thearbor. .The opening 33 transversely of the lap is larger than the endsof the key 3| to allow comparatively free play of the lap on the key,although rotary motion is of course transferred to the lap .by means ofthe key. By .means of this structure the lap may be changed end for endat will upon removal and re.- insertion of the key, and the lap isallowed to wobble and not maintain anyfixed path of revolution due tothe fixation of the path of revolution of the arbor. In this way theIapadjusts itself to the bore in the article being lapped.

In Fig. 5 an alternative structure for accomplishing this same purposeis shown and in this view an arbor 34 has thereon screw threads 35 whichflt loosely in screw threads 36 on thelap. Due to the intermittent andirregular movement of the arbor the loose screw threads allow the lap tohave a floating movement on the arbor and thus accomplish substantiallythe same result as the construction shown in Fig. 4.

iii)

in the lap 38 but the arbor 391s pressed in on both sides in two placesat right angles to each other as shown as 40, which allows resiliencyofthe arbor universally.

In Fig. '7 a sectioned lap is shownfor operating on an'open-endedarticle. In this connection the lap is made in two identical transversesections 4|, each section being a small cylinder and each section havingthree clutch faces-42 projecting form each end. These clutch faces andthe spaces allowed therebetween allow a loose connectionv whileimparting rotary movement between the sections of the lap. The arbor 43has similar clutch faces at its lower end and a rod 44 is threaded intothe arbor 43 and has at its lower end a nut 45 to hold the sectioned lapresiliently on the arbor while maintaining its rotation with the arbor.

Instead of using these clutch faces, loose screw threads 46 in thesections. of the lap, as shown in Fig. 9, may be used and these sectionsmay be fastened together by a bolt 48 loosely attaching them and theymay be attached to the'arbor 49 by means of the threaded member 50having thereon .a clutch face similar to that shown in Fig. 8 and thecircumference of which has a groove 5| therein, around which is a springwire ring 52. This clutch member also fits loosely to allow for playlaterally between the lap and the arbor. v

In Fig. 10 a clutch form of connection between arbor and lap is shownwhich might be used instead of the connection shown in Fig. 6. In thisview the clutch. portions 54 on the arbor 53 and 55, on the lap 56 arevcircumferentially grooved at 51 and in this groove is placed the springring 58.

Because of the reversible feature of the lap, uniformity of wear on thelap is produced and that uniformity promotes uniformity of lapping inthe article. By making the lap in two sections, eight variations ofarrangement of the lap on its arbor are available. If thelap shown inFig. 9 be considered and the respective ends of the sections be letteredas shown the following arrangements are possible:

A B A B C C D D B A B A D D c c C C D D B A 'A B' D D C C A B B A Bythis means both barrelling and spooling of both lap and bore are avoidedand the errors which creep in due to wear on the lap are symmetricallydistributed. I

This result is also furthered by the use of a lap s ightly shorter thana blind bore, in which, after the lap is completely inserted in thebore, it is reciprocated a few times near the blind end of the bore andwithout abrading the entranceand exit portion at the same time. Or, inthe same manner, with an open-ended bore, a lap longer than the bore maybe inserted beyond the entrance and exit end, and the further end of thebore abraded without abrading that entrance and exit end, or the boremay be reversed end for end.

It will of course be understood that in the use of the invention, witheach vertical-movement of the lap into the bore and the withdrawaltherefrom, only a very small amount of metal is removed and theinvention contemplates lapping each of the articles a number of times inany predetermined sequence this small amount. If the s'equence'werealways the same, due to the infinitesimal wear on the lap the articlesfinally lapped would be lapped less than those initially lapped, andtherefore this sequence must be varied and perhaps every other articlelapped in one course; and then the articles skipped lapped the next timearound or perhaps every third article may be lapped in onecircumferential trip around; and then another third picked up Y on thenext trip and the final third on the succeeding trip; or one group ofnine might be chosen and another group symmetrically around thecircumference of a plate might be lapped, and then the omitted articleswould be next lapped. By this process of lapping in a varied sequencethe errors which would creep in due to the wear on the lap may be madeinfinitesimally small and by varying the temperature between anysequence a larger or less amount of abrading may be accomplished by thecorresponding movements of the lap. Likewise, by varying the positionsofthe lap on its arbor further errors that creep in due to lap wear areeliminated and thus a multiplicity of uniform bores are produced whichhave the precise size originally desired.

It will of course be understood that certain of the processes of thisinvention may utilize the special lapping rod shown in Fig. 10 of myPatent 1,486,338, above referred to, or other similar mechanicallyexpanded laps. I

Furthermore, it is to be understood that th particular forms ofapparatus shown and described and the particular procedures .set forth,are presented for purposes of explanation and illustration and thatvarious modifications of said apparatus and procedures can be madewithout departing from the invention as defined in the appended claims.

The claims herein relate to lapping'or abrading tools. In two otherapplications, divisions in part of this one, I claim the apparatusherein disclosed and the method of lapping or grinding herein disclosed,respectively.

- What is claimed is: I.

1. A lapping tool comprising, in combination, a supporting memberadapted to be rotated and reciprocated during a finishing operation, alongitudinally and circumferentially homogeneous lap having a continuouscylindrical surface, whereby said lap .varies uniformly in circumferencewith variations of temperature, and means in said lap and on saidsupporting member to attach the same together to allow either end ofsaid lap to be made the leading end including interlocking means toprevent relative rotation between said lap and member.

2. A lapping tool comprising, in combination, a supporting memberadapted to be rotated and reciprocated during a finishing operation, alongitudinally and circumferentially homogeneous lap having a continuouscylindrical surface, whereby said lap varies uniformly in circumferencewith variations of temperature, and means in said lap and on saidsupporting member to attach the same together to allow either end ofsaid lap to'be made the leading end, and to allow a measure of lateralmovement of said lap with respect to said support including interlockingmeans to prevent relative rotation between said lap and member.

3. A lapping tool comprising, in combination, a

supporting member adapted to be rotated, and reciprocated during afinishing operation, a longitudi'nally and circumferentially homogeneouslap having a continuous cylindrical surface, whereby said lap variesuniformly in circumference with variations of temperature, and composedof transverse sections, and-means to attach said sections and supportingmember together, to allow either end of said lap and of said sections tobe made the leading end including interlocking means to prevent relativerotation between said member, lap and sections.

4. A lapping tool comprising, in combination, a supporting memberadapted to be rotated, and

amama reciprocated during a finishing operation, a longitudinally andcircumferentially homogeneous lap having a continuous cylindricalsurface, whereby said lap varies uniformly in circumference withvariations of temperature, and composed of transverse sections, andmeans to attach said sections and supporting member together, to alloweither end of said lap and of said sections to be made the leading end,and to allow a measure of lateral movement of said lap with respect tosaid support including interlocking means to prevent relative rotationbetween said member, lap and sections.

WI LIAM E. HOKE.

